Self-cooled rocket nozzle



R. F. THIELMAN SELF-COOLED ROCKET NOZZLE Feb. 2, 1965 I Filed April 24. 1961 INVENTOR. ujsell Hie/Mall BY v we "LMTTORNEYS dnl United States Patent 3,167,909 SELF-QOQLED ROCKET NOZZLE Russeil F. Thieiman, Cleveland, Ohio, assignor to Thompson Raine Wooldridge Inc, Cleveland, Ohio, at corporation of ()hio Filed Apr. 24, 1961, Ser. No. 185,120 4 Claims. (Cl. 60-356) This invention relates to reaction motor discharge nozzles for missiles, rockets and related air and space borne vehicles, and is more particularly directed to improved methods and means for cooling the discharge nozzle during operation of the motor.

Heretofore difiiculties have been encountered in cooling discharge nozzles particularly the throat areas thereof.

Certain refractory metals have been employed in the throat area of such nozzles to Withstand the thermal environment and to maintain throat contour or profile. However, the melting point of the refractory metals places an undue limitation on the maximum temperature a propellant may reach. Furthermore, when rocket exhaust gas products produce an oxidizing atmosphere, some refractory inserts react to form a low melting point oxide thus further reducing the maximum allowable operating temperature of the propellant employed. In addition, integral solid refractory metal throat inserts are diameter limited due to the present day state of manufacturing and cost.

Advanced high temperature rocket propellants produce thermal environments of sufiicient severity to cause increasing problems in the materials of construction used for the nozzle, particularly the nozzle throat area. Optimum propellant performance during operation de mands maintenance of the rocket nozzle contour dimensions, particularly in the throat area. It is well known that in the throat area the thermal environment is most severe and is the location wherein deleterious heat effects are most likely to occur.

Thus a need presently exists for a throat insert which is independent of the aforementioned limitations.

By employment of the present invention I substantially overcome the problems and diificulties of the prior art and provide a nozzle throat assembly simple and cornpact in construction and efiicient in operation.

It is therefore an object of the present invention to provide improved means for cooling discharged nozzles of reaction motors employed with missiles, rockets and related air and space borne vehicles.

Another object of the present invention is to provide improved means for insulating the internal wall of discharge nozzles of reaction motors from the high temperature of the exhaust gases flowing through the nozzle.

Another object of the present invention is to minimize ablation of the nozzle wall caused by the high temperature of the exhaust gases flowing through the nozzle.

A further object of the present invention is to provide an improved throat insert which provides a layer of cooling gases which insulates the nozzle wall from the hot gases and minimizes heat transfer to the nozzle wall from the gases.

A still further object of the present invention is to provide an improved method of insulating the nozzle wall from hot exhaust gases by providing an insulating layer of cool gases which minimize heat transfer to the nozzle wall.

These and other objects, features and advantages of the present invention will become readily apparent from a careful consideration of the following detailed description when considered in conjunction with the accompanying drawings wherein like reference numerals and characters refer to like and corresponding parts throughout the several views.

3,1619% Patented Feb. 2, 1965 On the drawing:

FIGURE 1 is a fragmentary elevational view in partial section illustrating a plurality of cooling units forming a nozzle throat insert assembly.

FIGURE 2 is an enlarged fragmentary view of FIG- URE 1 illustrating the details of a cooling unit.

FIGURE 3 is an enlarged fragmentary view in section taken along lines IIIIII of FIGURE 1.

FIGURE 4 is a fragmentary view in cross section illustrating an integral throat insert having a plurality of spaced cooling chambers.

As shown on the drawings:

Briefly stated, the present invention comprises a nozzle insert assembly, generally indicated by the numeral 5. The assembly 5 comprises a plurality of separate units 6, each of which units is chambered as at 7 to receive a coolant, generally indicated by the numeral 8 which, at ambient temperature and pressure, is a solid material, such as lithium hydride.

The coolant 8 is preferably in powdered form and is packed in chamber 7, or when heated to a molten state is solidified in chamber 7. The coolant may be introduced through an inlet 9 formed in an end wall 10 of the unit 6.

As appears in FIGURES 2 and 3, each module unit 6 comprises the inlet wall 10 and opposed end wall 11. The top wall 12 is provided with an outer surface 12a contoured to the complementary surface 13 of the section of the nozzle wall 14 adjacent thereto.

As appears in FIGURE 1, a plurality of the units 6 are annularly arranged to provide a throat insert assembly in a discharge nozzle of .a reaction motor (not shown). The reaction motor nozzle is generally indicated by the numeral 15 and comprises a gas entrance portion 16 through which gas flows in the direction indicated by the arrow into a throat portion 17 defined by the plurality of units 6 and a diverging nozzle exit portion 18. The wall 19 of the nozzle is provided with a shoulder 20 against which the end walls 11 of the plurality of units 6 abut to maintain the units 6 in position. An annular ring 21 of refractory material is seated in a groove formed in nozzle wall 19 blocking the inlets 10 of each unit 6 and is provided with an internal contour to assure surface continuity between the nozzle entrance portion 16 and the inner or bottom wall 22 of each unit 6. The nozzle may comprise a two-piece construction including an outer rigid wall 23 having an outturn flange 24 in face contact with a completementary outturned flange 25 of a rigid outer annular sleeve 26 secured to the wall 19 adjacent the throat to increase the strength of the nozzle. The flanges 24 and 25 may be secured as by a plurality of bolts 27.

Referring to FIGURE 2, each of the side Walls 30 and 31 are shaped relative to the complementary side walls 32 and 33 respectively of the adjacent unit 6 to assure a close leakproof fit at the parting line 34 therebetween. As shown in FIGURE 2, when the units 6 are employed as a nozzle throat insert, the opposed side walls 31 and 31 of each unit may be divergingly tapered from the bottom wall 22 to the top wall 12. The top wall 12 preferably is arcuate to correspond, as aforesaid, to the contour of the surface 13 of the nozzle wall 19.

The bottom wall 22 of each unit 6 has a plurality of apertures 35 formed therein which may be equally spaced, randomly spaced, and parallel and axial spacing of the apertures are contemplated within the scope of the present invention.

The bottom wall 22 of each unit is provided with an exterior contour as at 22a in such a manner that the units when assembled in annular form defines the nozzle interior surface desired with surface continuity between the adjacent nozzle wall portions to assure uniformvand streamline flow of the gases through the nozzle.

Each unit 6 is constructed of a refractory metal and is relatively thin walled when compared with the thickness of the Wall of the nozzle.

Under normal engine. operating conditions, reaction motor exhaust gases flow from the motor and are ex panded in passing through and out of the nozzle. Upon entering the throat, exhaust velocities are subsonic and a boundary layer 40 of exhaust gases is developed which limits heat transfer from the exhaust gases to thesurrounding nozzle structure. As the exhaust gases approach the throat section, however, the gas velocity increases approaching sonic velocity at thethroat. Correspondingly, as the exhaust gas velocity increases, the thickness of the protective boundary layer of exhaust gases de creases and thus, less resistance to heat transfer to the nozzle throat occurs.

Because of thehigh heat transfer experienced in the throat area, the throat surface or wall heats rapidly and presents a critical design problem.

When the units or segments 6 are formed to provide an annular throat insert, the heat of the exhaust gases is conducted tothe solid coolant therein along the bottom wall and side walls of each unit 6. The solid coolant begins to melt or become molten. When the coolant portion which contacts the bottom wall 22 reaches a given temperature under the ambient pressure, gases are generated from the coolant which form an internal pressure in the chamber 7 greater than the static pressure of the exhaust gas stream flowing through the nozzle. The

developed pressure gradient is sufficient to enable the gases to escape from the chamber 7 by passing through the cooling gas discharge ports 35. The gases leaving the ports 35, form a cooling film 36 covering the bottom wall 22 of the unit 6. The mean cooling film from each unit 6 provides an insulating envelope surrounding the hot exhaust gases passing through the throat.

It will be appreciated that the normal cooler boundary layer of the exhaust gases is augmented in thickness and cooled further thus reducing heat transfer to the throat of the nozzle. In addition the film protects the throat from reacting with the oxidizing, or reducing, environment caused by the exhaust gases contacting the throat surfaces thus preventing the formation of low melting point refractory oxides.

It will be appreciated that the present invention does not involve transpiration cooling in the sense that it is well known in the art today. The distinction is apparent in that the cooling eflfect of the gases generated from the solid material or coolant is a function of the temperature of the exhaust gases at the throat adjacent the outletsof the chambers 7. That is to say, as the temperature of the throat insert increases, the formation of cooling gases similarly accelerates to increase the film protection. In addition, the temperature rise experienced in the units 6 produces the'rmal'expansion of the pressurizable chamber walls which serves to lock the units 6 tightly in place.

A multi-phase coolant may be employed, such as lithium hydride, which after evolving gas, liquifies and vaporizes thus absorbing additional heat in the vicinity of the throat.

In FIGURE 4 there is illustrated an integral annular throat sleeve which is provided with a plurality of spaced pressurizable chambers each havinga common wall 38. The apertures 35 are formed in a similar manner and the coolant housed in the chambers 7.

From the foregoing it will be appreciated that among the advantages ofthe present invention are those involving the independence of the invention with respect to the throat diameter of the nozzle with which the insert is employed. Since theunits 6 are modules or building since such costs are independent of the number of modules used. Material costs are minimized since each module or unit requires only a minimum of finished stock. In contrast, approximately of the material employed in the conventional disc type throat insert must be discarded since only the outer portion thereof is employed.

Thus, it will be appreciated that by employment of the present invention, simple and efietcive means are provided for cooling nozzle areas where desired.

Although various minor modifications of the present invention will becomereadily apparent to those skilled in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such embodiments as reasonably and properly fall within the scope of my contribution to the art.

I claim as my invention:

1. A stationary insulating self-cooling insert assembly adapted for protecting reaction motor gas discharge nozzles from the effects of high temperature exhaust gases generated in the motor comprising: a plurality of units sized relative to each other and to-the adjacent nozzle wall portions to provide a predetermined surface continuity therebetween for minimizing directional disturb ances tin exhaust gases flowing adjacent thereto, each of said units including a housing having a pressurizable chamber, said housing having a pair of end walls sized to the nozzle wall, one of the end walls having an inlet for filling the chamber with a solid coolant material which converts to a gas at the operating temperature of the exhaust gases, a housing top wall sized to conform to the adjacent nozzle wall, a housing bottom wall having its outer surface shaped to'conform to the shape of the inner surfaces of the adjacent nozzle wall portions to provide a predetermined surface continuity therebetween for minimizing directional disturbances in the flow of exhaust gases adjacent thereto, a plurality of apertures formed in said bottom wall for discharge of gases generated from the coolant material to provide a heat transfer barrier between said bottom wall and the adjacent flowing exhaust gas stream, and housing side walls sized to conform to adjacent side walls of like units.

2. A. stationary insulating self-cooling insert assembly adapted for protecting reaction motor gas discharge nozzle walls from the effects of high temperature exhaust gases generated .in the motor comprising: a plurality of adjacent units sized relative to each other and to the adjacent nozzle wall portionsto provide a predetermined surface continuity therebetween for providing a'uniform exhaust gas flow path, each of said units including a housing having a pressurizable chamber adapted to contain solid coolant material which converts to a gas at the operating temperature of the exhaust gases, the housing having a pair of spaced end walls sized to the nozzle wall, one of the end walls having an inlet for filling the chamber with said coolant material, a housing top wall sized toconform to the nozzle wall, a housing bottom wall having its outer surface shaped to conform to the shape of the inner surfaces of the adjacent nozzle wall portions to provide a predetermined surface continuity therebetween for minimizing directional disturbances in the flow of exhaust gases adjacent thereto, apertures formed in said bottom Wall for discharge of gases generated from the coolant material to provide a heat transfer barrier between said bottom wall and the adjacent flowing exhaust gas stream, and side Walls convergingly tapered, from the bottom wall to the top wall to conform to the adjacent side Walls of like units.

3. A stationary insulating self-cooling insert assembly adapted for protecting reaction motor gas discharge nozzles from'the effects of high temperature exhaust gases generated in the motor comprising: a plurality of units sized relative to each other and to the adjacent nozzle wall portions to provide a predetermined surface continuity therebetween for minimizing directional disturbances in exhaust gases flowing adjacent thereto. each of said units including a housing having a pressurizable chamber adapted to contain a solid coolant material which converts to a gas at the operating temperature of the exhaust gases, said housing having a pair of end walls sized to the nozzle wall, a housing top wall sized to conform to the adjacent nozzle wall, a housing bottom wall having its outer surface shaped to conform to the shape of the inner surfaces of the adjacent nozzle wall portions to provide a predetermined surface continuity therebetween for minimizing directional disturbances in the flow of exhaust gases adjacent thereto, a plurality of apertures formed in said bottom wall for discharge of gases generated from the coolant material to provide a heat transfer barrier between said bottom wall and the adjacent flowing exhaust gas stream, and housing side walls sized to conform to adjacent side walls of like units.

4. A stationary insulating self-cooling insert assembly adapted for protecting reaction motor gas discharge nozzles from the effects of high temperature exhaust gases generated in the motor comprising: an annular sleeve sized relative to the adjacent nozzle wall portions to provide a predetermined surface continuity therebetween for minimizing directional disturbances in exhaust gases flowing adjacent thereto, said sleeve having a plurality of pressurizable chambers, said sleeve having a pair of end walls sized to the nozzle wall, one of the end Walls having inlet means for filling the chambers with solid coolant material which converts to a gas at the operating temperature of the exhaust gases, a sleeve outer wall sized to conform to the adjacent nozzle wall, a sleeve inner wall having its outer surface shaped to conform to the shape of the inner surfaces of the adjacent nozzle wall portions to provide a predetermined surface continuity therebetween for minimizing directional disturbances in the flow of exhaust gases adjacent thereto, and a plurality of apertures formed in said sleeve inner wall communicating with the pressurizable chambers for discharge of gases generated from the coolant material to provide a heat transfer barrier between said sleeve inner wall and the adjacent flowing exhaust gas stream.

References Cited in the file of this patent UNITED STATES PATENTS 3,005,308 Bader Oct. 24, 1961 3,005,338 Libby et a1 Oct. 24, 1961 3,014,353 Scully et a1 Dec. 26, 1961 3,022,190 Feldman Feb. 20, 1962 3,103,885 McLauchlan Sept. 17, 1963 3,115,746 Hsia Dec. 31, 1963 3,122,883 Terner Mar. 3, 1964 OTHER REFERENCES The Role of Solids Is Growing, by Frank G. McGuire, Missiles and Rockets, July 27, 1959, pages 31-33, vol. 5, No. 31. 

1. A STATIONARY INSULATING SELF-COOLING INSERT ASSEMBLY ADAPTED FOR PROTECTING REACTION MOTOR GEAR DISCHARGE NOZZLES FROM THE EFFECTS OF HIGH TEMPERATURE EXHAUST GASES GENERATED IN THE MOTOR COMPRISING: A PLURALITY OF UNITS SIZED RELATIVE TO EACH OTHER AND TO THE ADJACENT NOZZLE WALL PORTIONS TO PROVIDE A PREDETERMINED SURFACE CONTINUITY THEREBETWEEN THE MINIMIZING DIRECTIONAL DISTURBANCES IN EXHAUST GASES FLOWING ADJACENT THERETO, EACH OF SAID UNITS INCLUDING A HOUSING HAVING A PRESSURIZABLE CHAMBER, SAID HOUSING HAVING A PAIR OF END WALLS SIZED TO THE NOZZLE WALL, ONE OF THE END WALLS HAVING AN INLET FOR FILLING THE CHAMBER WITH A SOLID COOLANT MATERIAL WHICH CONVERTS TO A GAS AT THE OPERATING TEMPERATURE OF THE EXHAUST GASES, A HOUSING TOP WALL SIZED TO CONFORM TO THE ADJACENT NOZZLE WALL, A HOUSING BOTTOM WALL HAVING ITS OUTER SURFACE SHAPED TO CONFORM TO THE SHAPE 